Chemical mechanical polishing compositions for step-ll copper line and other associated materials and method of using same

ABSTRACT

A CMP composition and process for planarization of a semiconductor wafer surface having a copper barrier layer portion, said composition comprising an oxidizing agent, a boric acid component, and an abrasive.

FIELD OF THE INVENTION

The present invention relates to a chemical mechanical polishing slurryfor surfaces of a semiconductor wafer, and more particularly, to achemical mechanical polishing slurry and a method for using the slurryto remove and polish copper, barrier materials and dielectric materialslayered on semiconductor wafer surfaces.

DESCRIPTION OF THE RELATED ART

Semiconductor wafers are used to form integrated circuits. Thesemiconductor wafer includes a substrate, such as silicon, into whichregions are patterned for deposition of different materials havinginsulative, conductive or semi-conductive properties.

In order to obtain the correct patterning, excess material used informing the layers on the substrate must be removed. Further, tofabricate functional and reliable circuitry, it is important to have aflat or planar semiconductor wafer surface. Thus, it is necessary toremove and/or polish certain surfaces of a semiconductor wafer.

Chemical Mechanical Polishing or Planarization (“CMP”) is a process inwhich material is removed from a surface of a semiconductor wafer, andthe surface is polished (planarized) by coupling a physical process suchas abrasion with a chemical process such as oxidation or chelation. Inits most rudimentary form, CMP involves applying slurry, a solution ofan abrasive and an active chemistry, to a polishing pad that buffs thesurface of a semiconductor wafer to achieve the removal, planarization,and polishing process. It is not desirable for the removal or polishingprocess to be comprised of purely physical or purely chemical action,but rather the synergistic combination of both in order to achieve fastuniform removal. In the fabrication of integrated circuits, the CMPslurry should also be able to preferentially remove films that comprisecomplex layers of metals and other materials so that highly planarsurfaces can be produced for subsequent photolithography, or patterning,etching and thin-film processing.

Recently, copper has been used for metal interconnects in integratedcircuits. FIG. 1 shows an illustration a copper damascene processingstep in a semiconductor fabrication step. The layers that must beremoved and planarized include copper layer 12, (about 1-1.5 μm thick)on top of a thin copper seed layer 14, (about 0.05-0.15 μm thick). Thesecopper layers are separated from the dielectric material surface by alayer of barrier material 18, (about 50-300 Å thick) which preventsdiffusion of copper into the oxide dielectric material 16. The key toobtaining good uniformity across the wafer surface after polishing is byusing a slurry that has the correct removal selectivities for eachmaterial. If appropriate material removal selectivity is not maintained,unwanted dishing of copper and/or erosion of the dielectric material mayoccur.

Dishing occurs when too much copper is removed such that the coppersurface of a feature is recessed relative to the dielectric surface ofthe semiconductor wafer. Dishing primarily occurs when the copper andcopper-barrier (also referred to as copper-liner) material removal ratesare disparate. Oxide erosion occurs when the dielectric material removalrate is locally much higher than the surrounding field material. Dishingand oxide erosion are dependent on area, wafer pattern and pitch.

Due to the difference in chemical reactivity between copper and barrierliner materials, two chemically distinct slurries are often used in thecopper CMP process. The first step slurry (Step-I) is typically used torapidly planarize the topography and to uniformly remove the excesscopper, with the polish stopping at the barrier layer. The second stepslurry (Step-II) typically removes the copper-liner material at a highremoval rate and stops on the dielectric layer, or alternatively on acap layer that has been applied to protect the oxide.

U.S. patent application Ser. No. 10/315,641 for “Passivative ChemicalMechanical Polishing Composition for Copper Film Planarization” and“Improved Chemical Mechanical Polishing Compositions for Copper andAssociated Materials and Method Using Same” concurrently filed herewithand both incorporated herein by reference in their respectiveentireties, teach novel Step-1, planarization compositions useful forremoving and planarizing copper surfaces.

One object of this invention therefore is to provide a Step-II, CMPcomposition, for barrier or liner removal and planarization of a wafersurface after a Step-I polishing step of a CMP process for removal ofcopper overburden.

It is a further object of the present invention to provide a Step-II,CMP composition, for barrier or liner removal and planarization of awafer surface after a Step-I polishing step of a CMP process, which usesthe copper removal compositions disclosed in the U.S. patentapplications identified hereinabove.

A further object of the present invention is to provide a Step-II copperCMP slurry, which enables a high removal rate of barrier material, whileminimizing unwanted dishing of copper and/or erosion of dielectricmaterial.

A further object of this invention is to provide a Step-II CMP slurryhaving appropriate materials selectivity so as to minimize copperdishing and oxide erosion in a semiconductor wafer surface, therebyproviding a viable CMP approach to advanced device manufacturing.

These and other objects and advantages of the invention will be apparentto those skilled in the art upon reading the following detaileddescription and upon reference to the drawings.

SUMMARY OF THE INVENTION

The present invention relates to a CMP slurry composition and processdesigned to planarize barrier materials such as tungsten nitride,tantalum, tantalum nitride, silicon doped tantalum nitride, titaniumnitride and silicon doped titanium nitride, which are associated with acopper CMP process step. And as broadly disclosed herein, the CMP slurrycomposition, when used in a copper damascene planarization step, reducesthe occurrence of copper dishing and dielectric or oxide erosion whilecontrolling the rates at which both dielectric and barrier materials areremoved.

In one aspect, the invention relates to a CMP composition forplanarization of a wafer surface having a copper barrier layer portion,in which the CMP composition includes an oxidizing agent, a boric acidcomponent, and an abrasive.

In a further aspect, the invention relates to a method of planarizing awafer surface having a copper-barrier, liner portion, a copper portion,and a dielectric portion, said method comprising contacting the wafersurface, under CMP conditions, with a composition having a high removalrate on copper-barrier, liner, and a removal rate on the dielectricportion that is based on the concentration of a boric acid component inthe CMP composition.

Other aspects, features and embodiments of the invention will be morefully apparent from the ensuing disclosure and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an illustration of a copper damascene processing step-in asemiconductor fabrication step.

FIGS. 2(a)-2(d) show a two-step CMP process for planarizing a wafersurface after a copper damascene processing step.

FIG. 3 shows a plot of zeta potential and conductivity with respect topH for a silica abrasive according to one embodiment of the presentinvention.

FIG. 4 shows a graph plotting the step height reduction from thedielectric field area into the copper line array according to a furtherembodiment of the present invention.

FIG. 5 shows a plot of removal rates for Ta (liner material) and SiO₂(dielectric material) from a wafer surface according to a furtherembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION, AND PREFERRED EMBODIMENTS THEREOF

In CMP slurries it is advantageous to independently control the relativepolishing rates between the different materials of the pattern to bepolished. For example, in copper polishing one will actually polishcopper, liner/barrier materials such as Ta, TaN, Ti, TiN, TiW, WN andsilicon doped nitrides as well as dielectrics such as SiO₂, TEOS, PSG,BPSG, or any low-K dielectric.

FIG. 2(a) shows an illustration of a copper filled feature after acopper damascene processing step where copper 12, fills feature 14,previously etched into dielectric material 16, by a damascene processingstep. A barrier liner 18 deposited prior to copper fill, preventsdiffusion of copper into dielectric material 16. In a first CMP processstep, often referred to as Step 1, the bulk of the copper topographywill be planarized to at or just above the barrier liner as shown inFIG. 2(b). In some cases, the planarization Step-I will proceed untilexposure of the barrier liner, and the Step 1 formulation having a highselectivity for copper, will cause the copper material to dish slightlybelow the topography of barrier liner 18, as shown in FIG. 2(c). In afinal planarization step, commonly referred to as a Step II process, thebarrier liner 18, must be removed and planarized such that thedielectric, barrier and copper lie within the same plane, as shown inFIG. 2(d). To accomplish the Step-II process, a second CMP processingstep employing a CMP composition different from that of Step I, is used.Typically, the Step II process removes the barrier liner 18, and often athin layer (e.g. 300 Å) of the dielectric material 16. The compositionused in the Step II, CMP processing step, is the subject of the presentinvention.

The present invention provides a novel composition useful for removingand planarizing the materials associated with a Step II, CMP process.More specifically, the present invention provides a novel compositionuseful in the planarization of a wafer surface having copper, liner anddielectric components therein. The novel composition comprises a boricacid component, the concentration of which, advantageously affects theremoval rate and thus the selectivity of the dielectric material

The invention is based on the discovery that addition, to a CMPcomposition, of boric acid and/or a derivative thereof, results in astable slurry formulation having tunable selectivity to dielectricmaterials. Advantageously, the removal rate of the dielectric materialcan be tuned or controlled by adjusting the concentration of the boricacid component(s) in the CMP composition.

Accordingly, in one embodiment, the present invention relates to a StepII, CMP composition for use in planarizing the topography of a wafersurface after a copper damascene, Step I, CMP polishing step. Thecomposition, comprising an abrasive, and a boric acid component andoptionally an oxidizing agent, is useful for leveling the wafer'stopography, which may comprise any one of copper, liner and dielectricmaterials. The boric acid component in the CMP composition serves topassivate the dielectric material during a CMP, Step II process.

As used herein, the term “boric acid component” is intended to includeboric acid, its salts and derivatives, including but not limited to:alkyl substituted borates such as, ammonium tetraphenylborate(C₆H₅)₄BNH₄, phenylboric acid C₆H₅B(OH)₂, and trimethylboroxineC₃H₉B₃O₃, polyborates such as, ammonium pentaborate octahydrate(NH₄)₂B₁₀O₁₆.8H₂O, ammonium tetraborate tetrahydrate (NH₄)₂B₄O₇.4H₂O,and potassium tetraborate tetrahydrate K₂B₄O₇.4H₂O, fluoride substitutedborates such as, fluoroboric acid HBF₄, ammonium and tetrafluroborateNH₄BF₄, esters of boric acid such as, trimethylborate (CH₃O)₃B, andtriethylborate (C₂H₅O)₃B, and oxidation and dehydration products ofboric acid such as, boron monoxide (BO)_(x), boric anhydride B₂O₃,potassium metaborate KBO₂, and sodium perborate NaBO₃.

As will become apparent from the discussion that follows, the stableStep II, slurry composition and corresponding process provide forremoval of material and polishing of semiconductor wafer surfaces withsignificantly no dishing or oxide erosion, with significantly no surfacedefects and good planarization efficiency. Further, the copper surfaceproduced by such a Step II process has minimal corrosion tendency.

The present invention provides a novel CMP composition, which when usedin a Step II, CMP process, provides for high removal rates of linerlayer material, and planarization of a wafer surface comprising copper,liner and dielectric materials.

In a further embodiment, the present invention relates to a Step II, CMPcomposition for use in planarizing the topography of a wafer surfaceafter a copper damascene, Step I, CMP polishing step, said compositioncomprising abrasive, oxidizing agent, and boric acid component in thefollowing composition ranges by weight, based on the total weight of thecomposition: abrasive 0-30 wt. %; oxidizing agent 0-30 wt. %; and boricacid component 0.01-20 wt. %said composition having tunable selectivity for liner and dielectricmaterials based on the concentration of the oxidizing agent and boricacid component respectively.

The CMP composition comprising abrasive, oxidizing agent and boric acidcomponent, provides for tunable selectivity and removal rates for bothdielectric and liner materials as disclosed hereinabove. Addition ofcorrosion inhibitor to the composition provides means by which tocontrol removal rate and selectivity of copper in the lines, vias andtrenches. As the removal rates and selectivities of the dielectric andbarrier are controllable by varying the concentration of the boric acidcomponent, and oxidizing agent respectively, the copper material removalrate and selectivity is tunable through varying the concentration of thecorrosion inhibitor. Hence, the present invention advantageously relatesto a CMP composition having copper, barrier and dielectric tunability.

The present invention, in a further embodiment, relates to a Step II,CMP composition for use in a Step II, CMP process, said compositioncomprising abrasive, oxidizing agent, corrosion inhibitor and boric acidcomponent. Such a composition allows for the independent modification ofremoval rates of copper, liner and dielectric component, withoutaffecting the removal rate of any other component. By such modification,the present invention provides for process control of the selectivity ofthe copper, liner and dielectric materials.

The CMP composition comprising abrasive, oxidizing agent, corrosioninhibitor and boric acid component, provides for tunable selectivity andremoval rates for copper, liner and dielectric materials. The removalrate and selectivity of the dielectric material are controllable byvarying the concentration of the boric acid component. The linermaterial removal rate and selectivity are tunable through varying theconcentration of the boric acid component and/or oxidizing agent and thecopper material removal rate is tunable by varying the concentration ofthe oxidizing agent and/or passivating agent Hence, the presentinvention broadly relates to a CMP composition having copper, liner anddielectric selectivity and tunability.

The CMP composition of the invention in a preferred embodiment is anaqueous slurry composition, comprising abrasive, oxidizing agent,corrosion inhibitor and boric acid component in the followingcomposition ranges by weight, based on the total weight of thecomposition: abrasive 0-30 wt. %; oxidizing agent 0-30 wt. %; boric acidcomponent 0.01-20 wt. % and corrosion inhibitor 0-10 wt. %

In a more preferred embodiment, the composition of the inventioncomprises a silica abrasive, hydrogen peroxide (H₂O₂) as oxidizingagent, and benzotriazole (BTA) as corrosion inhibitor, in the followingcomposition ranges by weight, based on the total weight of thecomposition: silica abrasive 0-30 wt. %; H₂O₂ 1-30 wt. %; BTA 0.01-10wt. %; and boric acid 0.1-5 wt. %

In a still more preferred embodiment, the CMP composition comprises thefollowing components by weight, based on the total weight of thecomposition: silica abrasive about 13 wt. %; H₂O₂ about 5 wt. %; BTAabout 0.4 wt. %; boric acid about 2.0 wt. % water about 79.6 wt. % andKOH negligible.with the total wt. % of all components in the composition totaling to100 wt. %. KOH is used as base in the above composition to adjust the pHof the CMP composition to about 6.0.

Table 1 shows a comparison of removal rates for a Ta liner material anda SiO₂ dielectric material, where the second composition shown in Row 2includes approximately 1 wt % boric acid. Advantageously, the additionof boric acid and/or derivatives thereof, provides means by which totune the selectivity and removal rate of the barrier material (Ta) tothe dielectric material (SiO₂). TABLE 1 Comparison of Step-II CopperPolishing Composition Having 1 wt % Boric acid. Removal Rate in Å/minSilica H₂O₂ Buffer Boric acid BTA (WIWNU in %) (wt. %) (wt. %) (wt. %)(wt. %) pH (wt. %) Ta SiO₂ Other 13 5 ˜2 0 6 0.1 1354 1036 Buffer 1253Phosphoric (85%) + KOH (45%) 13 5 ˜2 1 6 0.1 1331 504 Buffer as above

Table 1 evidences the advantage of boric acid addition to a CMPcomposition for Step II removal of liner material in acopper-planarization step, where a 1% addition of boric acid reduces thedielectric removal rate by half. TABLE 2 Comparison of Step II,Copper-liner Removal Rates by varying the concentration of oxidizingagent. (CMP conditions 3 psi downforce, 90 rpm table and quillvelocity.) Ta Removal Silica H₂O₂ Boric acid BTA Rate in Å/min (wt. %)(wt. %) (wt. %) pH (wt. %) (WIWNU in %) 13 1 1 6 0.1 264 13 10 1 6 0.1608

Table 2 shows a comparison of removal rates for a Ta liner material as afunction of oxidizing agent (H₂O₂) concentration. The liner removal rateof the CMP composition of the present invention may be independentlycontrolled by varying the concentration of the oxidizing agent as theoxidizing agent serves to oxidize the barrier material in thebarrier-polishing step.

The abrasive component as used herein may be of any suitable type,including, without limitation, oxides, metal oxides, silicon nitrides,carbides, etc. Specific examples include silica, alumina, siliconcarbide, silicon nitride, iron oxide, ceria, zirconium oxide, tin oxide,titanium dioxide, and mixtures of two or more of such components insuitable form, such as grains, granules, particles, or other dividedform. Alternatively, the abrasive can include composite particles formedof two or more materials, e.g., NYACOL® alumina-coated colloidal silica(Nyacol Nano Technologies, Inc., Ashland, Mass.). Alumina is a preferredinorganic abrasive and can be employed in the form of boehmite ortransitional δ, ε or γ phase alumina. Organic polymer particles, e.g.,including thermoset and/or thermoplastic resin(s), can be utilized asabrasives. Useful resins in the broad practice of the present inventioninclude epoxies, urethanes, polyesters, polyamides, polycarbonates,polyolefins, polyvinylchloride, polystyrenes, polyolefins, and(meth)acrylics. Mixtures of two or more organic polymer particles can beused as the abrasive medium, as well as particles comprising bothinorganic and organic components. In a preferred embodiment, theabrasive component of the present invention includes silica Morepreferably, the silica abrasive is of a colloidal or mono-disperse type,available commercially under a brand name such as LEVASIL®100CK/30%-TaHS₃ procuded by H.C. Starck GmbH, Leverkusen, Geb. G8,Germany.

The pH of the present CMP compositions may be at any suitable value thatis efficacious for the specific polishing operation employed. In oneembodiment, the pH of the CMP composition can be in a range of fromabout 2 to about 11, more preferably in a range of from about 2 to about7.0, and most preferably in a range of from about 3 to about 6.

FIG. 3 shows a plot of zeta potential and conductivity with respect topH for a silica mono-disperse abrasive having an approximate meanparticle size of 65 mm and a spherical morphology. The zeta potential ofa particle defines the electrostatic charge on that particle in aparticular liquid. In the case of the present invention, as solution pHincreases, silica abrasive zeta potential decreases.

Moreover, FIG. 3 further identifies Ta₂O₅ (by-product from oxidation ofTa barrier material with oxidizing agent) as having a positive zetapotential at pHs below around 6.5. The silica particle having a negativezeta potential of around −30 mV at a pH of around 6.0, willelectrostatically attract the Ta₂O₅ wafer surface having a positive zetapotential. And advantageously, the slurry composition of the presentinvention having a pH of around 6.0, will provide optimal conditions forthe dissolution of the oxidized tantalum.

The term oxidizing agent as used herein is defined as any substancewhich removes metal electrons and raises the atomic valence and includesbut is not limited to hydrogen peroxide (H₂O₂), ferric nitrate(Fe(NO₃)₃), potassium iodate (KIO₃), potassium permanganate (KMnO₄),nitric acid (HNO₃), ammonium chlorite (NH₄ClO₂), ammonium chlorate(NH₄ClO₃), ammonium iodate (NH₄IO₃), ammonium perborate H₄BO₃), ammoniumperchlorate H₄ClO₄), ammonium periodate (NH₄IO₃), ammonium persulfate(NH₄)₂S₂O₈), tetramethylammonium chlorite ((N(CH₃)₄)ClO₂),tetramethylammonium chlorate ((N(CH₃)₄)ClO₃), tetramethylammonium iodate((N(CH₃)₄)IO₃), tetramethylammonium perborate ((N(CH₃)₄)BO₃),tetramethylammonium perchlorate ((N(CH₃)₄)ClO₄), tetramethylammoniumperiodate ((N(CH₃)₄)IO₄), tetramethylammonium persulfate((N(CH₃)₄)S₂O₈), urea hydrogen peroxide ((CO(NH₂)₂)H₂O₂). The preferredoxidizing agent for the CMP slurry composition of the instant inventionis hydrogen peroxide.

Alternatively, the oxidizing agent may comprise an amine-N-oxide havingthe formula (R¹R²R³N→O), wherein R¹R²R³ are independently selected fromthe group consisting of: H, aryl, and C₁-C₈ alkyl. Specific examples ofamine-N-oxides include but are not limited to 4-methyhmorpholine N-oxide(C₅H₁₁NO₂) and pyridine-N-oxide (C₅H₅NO).

The term corrosion inhibitor as used herein, is intended to mean anysubstance that reacts with copper and/or oxidized copper thin film topassivate the copper layer and prevent excessive etching of the coppersurface during CMP. Preferably, the CMP composition of the presentinvention has a static metal etch rate of less than 500 Å, morepreferably less than 200 Å, and most preferably less than 50 Å.

The corrosion inhibitor component in the CMP composition of theinvention may comprise one or more inhibitor components including forexample, imidazole, aminotetrazole, benzotriazole, benzimidazole, amino,imino, carboxy, mercapto, nitro, alkyl, urea and thiourea compounds andderivatives, etc. Dicarboxylic acids such as glycine, oxalic acid,malonic acid, succinic acid, nitrilotriacetic acid, iminodiacetic acids,and combinations thereof are also useful corrosion inhibitors. Preferredinhibitors include tetrazoles and their derivatives. In a specificembodiment, the corrosion inhibitor is 5-aminotetrazole (ATA) orbenzotriazole (BTA).

The solvents employed in the CMP composition of the invention can besingle component solvents or multicomponent solvents, depending on thespecific application. In one embodiment of the invention, the solvent inthe CMP composition is water. In another embodiment, the solventcomprises an organic solvent, e.g., methanol, ethanol, propanol,butanol, ethylene glycol, propylene glycol, glycerin, etc. In yetanother embodiment, the solvent comprises a water-alcohol solution. Awide variety of solvent types and specific solvent media can be employedin the general practice of the invention to provide asolvating/suspending medium in which the abrasive is dispersed and inwhich the other components are incorporated to provide a composition ofappropriate character, e.g., of slurry form, for application to theplaten of the CMP unit to provide a desired level of polishing of thecopper on the wafer substrate.

Bases can be optionally employed for pH adjustment in compositions ofthe invention. Illustrative bases include, by way of example, potassiumhydroxide, ammonium hydroxide, tetramethylammonium hydroxide (TMAH),tetraethylammonium hydroxide, trimethyl hydroxyethylammonium hydroxide,methyl tri(hydroxyethyl)ammonium hydroxide, tetra(hydroxyethyl)ammoniumhydroxide, and benzyl trimethylammonium hydroxide.

Acids can also be optionally employed for pH adjustment and buffering inthe CMP compositions of the invention. The acids used can be of anysuitable type, including, by way of example, formic acid, acetic acid,propanoic acid, butanoic acid, pentanoic acid, isovaleric acid, hexanoicacid, heptanoic acid, octanoic acid, nonanoic acid, lactic acid,hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid,hydrofluoric acid, malic acid, fumaric acid, malonic acid, glutaricacid, glycolic acid, salicylic acid, 1,2,3-benzenetricarboxylic acid,tartaric acid, gluconic acid, citric acid, phthalic acid, pyrocatechoicacid, pyrogallol carboxylic acid, gallic acid, tannic acid, and mixturesincluding two or more acids of the foregoing or other types. In apreferred embodiment, the CMP composition of the present inventionincludes phosphoric acid.

Chelating agents when present are intended to mean any substance that inthe presence of a water containing solution solubilizes or etches theoxidized copper material. Copper chelating agents useful in the presentinvention include but are not limited to mineral acids (i.e.hydrochloric acid, nitric acid), inorganic acids (i.e. phosphoric acid)and organic acids and amino acids (i.e. glycine, citric acid, aceticacid and maleic acid). A preferred chelating agent is glycine.

Amines when present can be of any suitable type, including, by way ofexample, hydroxylamine, monoethanolamine, diethanolamine,triethanolamine, diethyleneglycolamine, N-hydroxylethylpiperazine,N-methylethanolamine, N,N-dimethylethanolamine, N-ethylethanolamine,N,N-diethylethanolamine, propanolamine, N,N-dimethylpropanolamine,N-ethylpropanolamine, N,N-diethylpropanolamine,4-(2-hydroxyethyl)morpholine, aminoethylpiperazine, and mixturesincluding two or more of the foregoing or other amine species.

Surfactants when optionally employed in the CMP compositions of theinvention can be of any suitable type, including non-ionic, anionic,cationic, and amphoteric surfactants, and polyelectrolytes including,for example: salts of organic acids; alkane sulfates (e.g., sodiumdodecyl sulfate); alkane sulfonates; substituted amine salts (e.g.,cetylpyridium bromide); betaines; polyethylene oxide; polyvinyl alcohol;polyvinyl acetate; polyacrylic acid; polyvinyl pyrrolidone;polyethyleneimine; and esters of anhydrosorbitols, such as thosecommercially available under the trademarks Tween® and Span®, as well asmixtures including two or more of the foregoing or other surfactantspecies.

The present invention in a further embodiment, provides a method forplanarizing a wafer surface having a copper-barrier, liner portion, acopper portion, and a dielectric portion, said method comprisingcontacting the wafer surface, under CMP conditions, with a compositionhaving a high removal rate on the copper-barrier, liner and a removalrate on the dielectric portion that is based on the concentration of aboric acid component in the CMP composition.

In a still further embodiment, the present invention provides a methodfor planarizing a wafer surface having a copper-barrier, liner portion,a copper portion, and a dielectric portion, said method comprisingcontacting the wafer surface, under CMP conditions, with a compositionhaving a high removal rate on the copper-barrier, liner and removalrates of the copper-barrier, liner, copper and dielectric portions thatare based on the concentration of at least one component in the CMPcomposition.

Preferably, the CMP composition of the present invention provides forselectivities of Cu:Ta:oxide of at least 1:10:10 and barrier linerremoval rates of at least 300 Å/min., more preferably at least 400Å/min. and most preferably at least 600 Å/min.

The CMP composition of the invention can be readily formulated in aso-called ‘day tank’ or ‘storage tank,’ or the CMP composition can beprovided as a two-part formulation or a multi-part formulation that ismixed at the point of use. The individual parts of the multi-partformulation can be mixed at the polishing table, polishing belt or thelike, or in an appropriate container shortly before reaching thepolishing table.

In one embodiment, the CMP composition of the present invention isformulated as a single-package shortly before reaching the polishingtable, according to the following process steps:

-   -   (a) combining de-ionized water and an acid component with an        abrasive component under vigorous mixing until pH of        approximately 2.5;    -   (b) adding boric acid component to step (a);    -   (c) adding corrosion inhibitor component to step (b);    -   (d) mixing step (c) for a period of time that is at least 1        hour;    -   (e) adding base or alkaline material to step (d) until pH of        approximately 6.0;    -   (f) adding oxidizing agent to step (e); and    -   (g) allowing (f) to age for approximately one hour prior to use        in CMP process.

In a more preferred embodiment, the CMP composition of the presentinvention is formulated as a single-package according to the followingprocess steps:

-   -   (a) combining de-ionized water and nitric acid with silica        abrasive under vigorous mixing until pH of approximately 2.5;    -   (b) adding boric acid component to step (a);    -   (c) adding benzotriazole to step (b);    -   (d) mixing step (c) for a period of time that is at least 1        hour;    -   (e) adding KOH to step (d) until pH of approximately 6.0;    -   (f) adding H₂O₂ to step (e); and    -   (g) allowing (f) to age for approximately one hour prior to use        in CMP process.

In all such embodiments, the mixing of ingredients or parts to form thefinal composition occurs in an appropriate container shortly beforereaching the polishing table, at the point of use, or with mixing at thepolishing table, polishing belt or the like.

The CMP composition of the present invention can be utilized in aconventional manner in CMP operation, by application of the CMPcomposition to the wafer surface in a conventional fashion, andpolishing of the surface can be carried out using a conventionalpolishing element such as a polishing pad, polishing belt, or the like.

Generally, the Step II, CMP copper slurry is applied to a pad containedon a polishing instrument. Polishing instrument parameters such as downforce (DF), flow rate (FR), table speed (TS), quill speed (QS), and padtype can be adjusted to effect the results of the CMP slurry. Theseparameters are important in obtaining efficient planarization resultsand limiting dishing and erosion. Although these parameters may bealtered, when used with the CMP slurry of the present invention, thestandard conditions used are DF of 3 psi, FR of 200 ml/min, TS of 90 rpmQS of 90 rpm and the IC 1000 pad type.

The CMP composition of the invention is advantageously employed topolish barrier, metal and dielectric surfaces of semiconductorsubstrates, without the occurrence of dishing or other adverseplanarization deficiencies in the polished wafer surface.

CMP slurry compositions of the invention are highly effective forStep-II copper polishing of semiconductor wafer substrates, e.g.,polishing of patterned copper wafers. The CMP compositions of theinvention can be readily prepared by mixing of ingredients in thedesired single-package or multi-part formulations, consistent with theforegoing discussion herein of single-package and multi-partformulations. The concentrations of the respective ingredients can bewidely varied in specific formulations of the CMP composition, in thepractice of the invention, and it will be appreciated that the CMPcomposition of the invention can variously and alternatively comprise,consist or consist essentially of any combination of ingredientsconsistent with the disclosure herein.

The features and advantages of the invention are more fully shown by theempirical examples and results discussed below.

EXAMPLE 1

Bulk copper overburden was removed from an 854 Reticle (854 CMP025)wafer manufactured by Sematech, Inc. using a Step I slurry compositionfor bulk copper removal. Copper lines were polished using the Step IIslurry composition outlined in Row 2 of Table 1 hereinabove. Carefulinspection with an optical microscope showed that all liner was removedevenly and uniformly within 30 s. To ensure that the Cu lines wereelectrically isolated and shorts eliminated, a thin layer of SiO₂(200-300 Å) was removed as well.

FIG. 4 shows a graph plotting the step height reduction from thedielectric field area into the copper line array pre and post linerpolish with the CMP slurry composition outlined in Row 2 of Table 1. Inaddition to removing the Ta liner the Step II CMP composition alsoplanarized the wafer surface. Dishing and Erosion measures the stepheight from the field area, unpatterned, open areas of the chip, intothe copper line arrays. The step height from pre to post liner polish isreduced by up to 400 Å for line arrays with a variety of line and spacerwidths.

EXAMPLE 2

FIG. 5 shows a plot of removal rates for a thin film of Ta (linermaterial) and SiO₂ (dielectric material) present on a Si wafer surfaceas a function of weight percent concentration of boric acid component ina CMP composition. The composition comprising 13 wt. % silica, 10 wt. %hydrogen peroxide, 0.1 wt % BTA, pH 6.0 and varying wt % boric acid. Atlow boric acid concentrations the material removal rates as shown arefairly low, too low to insure high wafer throughput in IC chipmanufacturing. Adding boric acid to the slurry increases both removalrates. However, the Ta removal rate shows a stronger increase withincreasing boric acid concentration. At 0.4% wt boric acid the increasein the SiO₂ removal rate has saturated, but the Ta removal rate is stillfurther increasing. This shows, that with the current Step 2formulation, containing boric acid, the polishing process is highlytunable by the boric acid content. Thus depending on the specific needsof a particular integration process the Ta and SiO₂ removal rates can beadjusted accordingly.

While this invention has been disclosed and discussed primarily in termsof specific embodiments thereof, it is not intended to be limitedthereto. Other modifications and embodiments will be apparent to theworker in the art.

1. A CMP composition for planarization of a wafer surface having acopper barrier layer portion, said composition comprising an oxidizingagent, a boric acid component, and an abrasive.
 2. The CMP compositionaccording to claim 1, where in said wafer surface further comprisescopper and a dielectric material.
 3. The CMP composition according toclaim 1, wherein said barrier layer portion comprises a materialselected from the group consisting of Ta, TaN, Ti, TiN, TiW, WN andsilicon doped nitrides.
 4. The CMP composition according to claim 2,further comprising a corrosion inhibitor.
 5. The CMP compositionaccording to claim 4, wherein said abrasive, oxidizing agent, boric acidcomponent and corrosion inhibitor are present in the followingcomposition ranges by weight, based on the total weight of thecomposition: abrasive 0.01 to 30 wt. %; oxidizing agent 1 to 30 wt. %;corrosion inhibitor 0.01 to 10 wt. %; and boric acid component 0.01 to10 wt. %.


6. The CMP composition according to claim 5, wherein said boric acidcomponent passivates the dielectric material.
 7. The CMP compositionaccording to claim 1 being stable.
 8. The CMP composition according toclaim 1, wherein said boric acid component is selected from the groupconsisting of:
 9. The CMP composition according to claim 1, wherein saidboric acid component is boric acid.
 10. The CMP composition according toclaim 5 providing for tunable selectivity and removal rates for bothdielectric and barrier materials.
 11. The CMP composition according toclaim 10, wherein the removal rate and selectivity of the dielectric arecontrollable by varying the concentration of the boric acid component.12. The CMP composition according to claim 10, wherein the barriermaterial removal rate and selectivity are tunable through varying theconcentration of the oxidizing agent.
 13. The CMP composition accordingto claim 5, comprising the following ranges by weight, based on thetotal weight of the composition: silica abrasive 0 to 30 wt. %; H₂O₂ 1to 30 wt. %; BTA 0.01 to 10 wt. %; and boric acid 0.01 to 10 wt. %


14. The CMP composition according to claim 5, comprising the followingcomponents by weight, based on the total weight of the composition:silica abrasive about 13 wt. %; H₂O₂ about 5 wt. %; BTA about 0.4 wt. %;boric acid about 2.0 wt. % water about 79.6 wt. %

with the total wt. % of all components in the composition totaling to100 wt. %.
 15. The CMP composition according to claim 1, wherein saidabrasive component is selected from the group consisting of: oxides,metal oxides, silicon nitrides, and carbides.
 16. The CMP compositionaccording to claim 1, wherein said abrasive component is a silicamono-disperse abrasive having an approximate mean size of 65 nm and aspherical morphology.
 17. The CMP composition according to claim 1,having a pH in a range of from about 2 to about
 7. 18. The CMPcomposition according to claim 1, wherein said oxidizing agent isselected from the group consisting of: hydrogen peroxide (H₂O₂), ferricnitrate (Fe(NO₃)₃), potassium iodate (KIO₃), potassium permanganate(KMnO₄), nitric acid (HNO₃), ammonium chlorite (NH₄ClO₂), ammoniumchlorate (NH₄ClO₃), ammonium iodate (NH₄IO₃), ammonium perborate(NH₄BO₃), ammonium perchlorate (NH₄ClO₄), ammonium periodate (NH₄IO₃),ammonium persulfate ((NH₄)₂S₂O₈), tetramethylammonium chlorite((N(CH₃)₄)ClO₂), tetramethylammonium chlorate ((N(CH₃)₄)ClO₃),tetramethylammonium iodate ((N(CH₃)₄)IO₃), tetramethylammonium perborate((N(CH₃)₄)BO₃), tetramethylammonium perchlorate ((N(CH₃)₄)ClO₄),tetramethylammonium periodate ((N(CH₃)₄)IO₄), tetramethylammoniumpersulfate ((N(CH₃)₄)S₂O₈), and urea hydrogen peroxide ((CO(NH₂)₂)H₂O₂).19. The CMP composition according to claim 1, wherein said oxidizingagent hydrogen peroxide.
 20. The CMP composition according to claim 5,wherein said corrosion inhibitor is selected from the group consistingof: tetrazoles such as imidazole, aminotetrazole, benzotriazole,benzimidazole, amino, imino, carboxy, mercapto, nitro, alkyl, urea andthiourea compounds and derivatives, dicarboxylic acids such as glycine,oxalic acid, malonic acid, succinic acid, nitrilotriacetic acid,iminodiacetic acids, and combinations thereof.
 21. The CMP compositionaccording to claim 5, wherein said corrosion inhibitor is benzotriazole.22. The CMP composition according to claim 1, further comprising asolvent.
 23. The CMP composition according to claim 22, wherein saidsolvent is selected from the group consisting of: water organic solventand combinations thereof.
 24. The CMP composition according to claim 5,further comprising a base for pH adjustment, wherein said base isselected from the group consisting of: potassium hydroxide, ammoniumhydroxide and tetramethylammonium hydroxide (TMAH), tetraethylammoniumhydroxide, trimethyl hydroxyethylammonium hydroxide, methyltri(hydroxyethyl)ammonium hydroxide, tetra(hydroxyethyl)ammoniumhydroxide, and benzyl trimethylammonium hydroxide.
 25. The CMPcomposition according to claim 24, wherein said base is KOH.
 26. The CMPcomposition according to claim 5, further comprising an acid for pHadjustment, wherein said acid is selected from the group consisting of:formic acid, acetic acid, propanoic acid, butanoic acid, pentanoic acid,isovaleric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoicacid, lactic acid, hydrochloric acid, nitric acid, phosphoric acid,sulfuric acid, hydrofluoric acid, malic acid, fumaric acid, malonicacid, glutaric acid, glycolic acid, salicylic acid,1,2,3-benzenetricarboxylic acid, tartaric acid, gluconic acid, citricacid, phthalic acid, pyrocatechoic acid, pyrogallol carboxylic acid,gallic acid, tannic acid, and mixtures including two or more acids ofthe foregoing.
 27. The CMP composition according to claim 26, whereinsaid acid is nitric acid.
 28. A method of planarizing a wafer surfacehaving a copper barrier layer portion, said method comprising contactingthe material of the copper barrier layer under CMP conditions, with acomposition effective for removing and planarizing barrier layermaterial, wherein the CMP composition includes an oxidizing agent, aboric acid component, and an abrasive.
 29. A method of synthesizing aCMP slurry composition comprising the steps of: (a) combining de-ionizedwater and an acid component with an abrasive component under vigorousmixing until pH of approximately 2.5; (b) adding boric acid component tostep (a); (c) adding corrosion inhibitor component to step (b); (d)mixing step (c) for a period of time that is at least 1 hour and; (e)adding base or alkaline material to step (d) until pH of approximately6.0; (f) adding oxidizing agent to step (e); and (g) allowing (f) to agefor approximately one hour prior to use in CMP process.